1. Field of the Invention
The present invention relates to a data security apparatus for providing protection of the contents of a ROM storing, e.g., game program data against any illegal execution, copy or analysis.
2. Description of the Related Arts
Early simple video game machines allowed users to play only a single video game realized by game program data stored in a memory fixedly arranged within the machine body. However, recently developed and widespread game machines tend to include a removable ROM which has stored game program data so that the users can play variously different games merely by replacing the ROM with another. Such a ROM can be of a cartridge type like a ROM cartridge in which a dedicated circuit is enclosed in a small case, or alternatively be in the form of a CD-ROM using an optical storage medium, which are fully utilized depending on their respective advantages.
The ROM cartridge or CD-ROM storing an extremely popular game program may be often marketed at a high price since the supply is unlikely to catch up with the demand for that article. For this reason, a case just goes on and on where the contents of the ROM are unlawfully copied and put on the market. Furthermore, in the case of arcade game machines in game centers, a ROM board composed of a circuit overlying a substrate is used as the game program storage ROM. Due to its removability from the machine body, such a ROM board may also be possibly subjected to a risk that the contents thereof are copied and stolen for business use.
In order to deal with this, typical ROM data undergo an analysis or copy limitation processing, while simultaneously the game machine is provided with a data security device for limiting the execution of a game program stored in the ROM which has not undergone that processing. Description will now be given of such a data security device, by way of example, fitted to a game machine for CD-ROM's.
First of all, data stored in a commonly marketed CD-ROM (hereinafter referred to as a commercial CD) have the following configuration. In a commercial CD 18, as shown in FIG. 7, game program data 18d are stored with the insertion of a special code 18a not permitting any analysis or copy without using a dedicated apparatus.
A computer of a commercial game machine, on the other hand, is equipped with a security check means for checking the presence or absence of the special code 18a in the commercial CD 18 to permit only a program with the special code 18a to be executed. Thus, as long as it is a regular commercial CD 18 with the special code 18a inserted therein, the execution of its program data 18d is permitted by the security check means so that the game program data 18d can be executed by use of the normal commercial game machine. Even though a commercial CD 18 includes illegally copied program data 18d, the special code 18a is not permitted to be copied onto the CD, and hence an attempt to execute the program data 18d within in the CD by a commercial game machine will be in vain due to the presence of the security check means.
Nevertheless, the conventional data security apparatus as described above involved the following problems. Although the contents of game program data are to be securely protected from any illegal copy, analysis or execution by persons not having a legitimate title, it is convenient for a regular developer of the game program (namely a person having the legitimate title) to ensure an easy execution of the contents since he must check at all times how the created game is executed. A machine used for the check is preferably a commercial one identical in type to the machines actually manipulated by users, rather than a dedicated one which would require an additional cost for fabrication. Also in terms of checking whether the game can be played with a pleasure from the users' viewpoint, it is desirable to perform the check with a commercial game machine.
As described hereinabove, however, the commercial game machine is typically fitted with the security check means for checking the presence or absence of a special code, with the result that the machine will not permit the execution of a game program without a special code under development. Moreover, the special code has an extremely complicated configuration so as to prohibit any analysis or copy, and hence will take significant time and labor to create. Accordingly, creation of a further special code, if needed each time a new game software is developed, might possibly delay the development of game programs.